But if the control if bigger than the list of items there is a gap at the bottom.

Then you have to pad the list with empty entries at the beginning.

And there will be scroll bars yes.

Hmm, then the control suddenly makes less sense to me
But then you have to make sure it's always scrolled to the bottom at the beginning. If you want a control that even behaves "normal" from an API point of view (scrollposition 0 => scrolled to the bottom), you'll have to build a custom control.